1. Field of the Invention
This invention relates to apparatus and method for the in-situ generation of dopants for manufacture of microelectronic devices, and more specifically the invention relates to delivering dopants in a simple, ready and effective manner to the deposition site, e.g., a chemical vapor deposition chamber or an ion implant device.
2. Description of the Related Art
In the manufacture of semiconducting materials and semiconductor devices, a variety of gaseous compounds, e.g., arsine, phosphine, hydrogen selenide, hydrogen telluride, tetrafluorogermanium, trifluoroantimony, trichloroindium, and other fluoride species, are employed as dopant source materials.
These dopant source materials typically are delivered as gaseous components in a carrier gas stream, such as nitrogen, helium, argon or other suitable gas, and the dopant then may be introduced to the material to be doped, as for example by MOCVD or ion implantation techniques. In ion implantation, the dopant species-containing gas stream is flowed into an arc chamber of the ion implanter device, to generate the ionic dopant species which are directed to the substrate for dopant implantation.
The above-mentioned gaseous compounds utilized as dopants are hazardous in character, and due to health and safety considerations, must be carefully handled in the semiconductor manufacturing facility.
In conventional practice, dopant species may be supplied in the semiconductor manufacturing plant as gaseous compounds dispensed from high pressure gas cylinders. With such high pressure gas cylinders, there is the associated danger of cylinder rupture, resulting in gross introduction of the hazardous gas into the ambient environment of the manufacturing facility. There is also a danger of leakage from such high pressure gas cylinders, due to defects and to damage to the cylinder heads, gas flow regulators, and associated flow circuitry.
As an example of the foregoing deficiencies of the use of high pressure gas cylinders, arsine is employed in the manufacture of silicon-based semiconductor devices as a dopant source material, for arsenic doping of epitaxial semiconductor films, at relatively low concentrations, on the order of from about 20 to about 100 ppm. Even though utilized in dilute gas mixtures for such applications, the arsine is typically provided in bulk pure form in high pressure gas cylinders, which as indicated entails the risk of rupture of and/or leakage from the cylinders, with the consequence of release of arsine into the surrounding environment in the manufacturing plant.
As an alternative to the conventional requirement of high pressure gas cylinders of arsine or other dopant source gases in the semiconductor manufacturing plant, it would be desirable to provide a liquid source compound for dopants such as arsenic, selenium, tellurium, etc., which would obviate such requirement.
Unfortunately, however, no suitable liquid source compounds for such dopants have been produced which yield semiconductor materials having desired superior electrical and structural properties.
The art has sought various solutions to this problem.
U.S. Pat. No. 5,518,528 issued May 21, 1996 to Glenn M. Tom and James V. McManus describes a storage and delivery system for gases, in which the gas to be dispensed is adsorbed on a physical sorbent medium and selectively dispensed by pressure differential desorption of the sorbate gas from the sorbent material.
U.S. Pat. No. 4,936,877 issued Jun. 26, 1990 to Steven J. Hultquist and Glenn M. Tom describes a dopant delivery system for semiconductor manufacture, in which a carrier gas is flowed through a contacting zone containing a permeable film through which the vapor-phase dopant constituent permeates into the contacting zone, to yield a product gas mixture comprising the vapor-phase constituent in the carrier gas.
It would be an advance in the art to provide an effective system for the on-site generation of dopant gas species.
It therefore is an object of the present invention to provide means and method for on-site generation of dopant gas species, which are of a simple, ready and efficient character.
It is another object of the present invention to provide an ion implantation system including in-situ generation of dopant gas species for the ion implantation process.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.